Sealant composition, article and method

ABSTRACT

A composition comprises a curable epoxy-containing material, a first thermoplastic polyurethane component, a curative for the epoxy-containing material, and optionally, a second thermoplastic polyurethane component that is different than the first thermoplastic polyurethane component. The compositions are useful for sealing discontinuities in a substrate surface, especially those found in motor vehicles. Sealant articles and methods of sealing discontinuities are also disclosed.

This application is a National Stage filing of an internationalapplication under 35 USC 371 of PCT patent application Ser. No.PCT/EP98/06323, filed Oct. 2, 1998, which was published under PCTArticle 21(2) in English.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to compositions for sealing discontinuities, forexample of the type found in motor vehicles, and to articles used insealing the discontinuities, as well as to methods of sealing thediscontinuities.

2. Description of the Related Art

Motor vehicles such as automobiles and trucks have metal joints andseams that must be sealed. One example is a generally non-planar overlapjoint formed by welding together the roof and the side panel of thevehicle to create a square U-shaped trough called a roof ditch. Watercollects in the roof ditch and then is drained away from the vehicle.

To prevent water from seeping through the joint it is necessary to sealit. It is often difficult to obtain a good seal, however, because thejoint is not planar. In addition, the width of the roof ditch typicallyvaries along its length, further complicating the ability to provide agood seal. Historically, a variety of materials have been used assealants to fill voids in motor vehicles and exclude dirt, moisture, andother undesirable materials.

Sealants have been supplied as liquid or solid materials depending uponthe demands of the application. In the automotive industry, forinstance, roof ditch joints are typically sealed using a paste-likeplastisol which is then painted, baked and cooled to room temperature.

Hot melt sealants are also used and are generally solid thermoplasticmaterials which quickly melt with heating and then form a firm bond oncooling. In use, a bead of molten liquid sealant is applied on the jointor seam, much in the way caulking is applied. A worker then brushes orlevels the material into a layer of relatively uniform thickness.Applying such a sealant takes skill and often results in a poorly sealedjoint or seam. Hot melt sealants cannot be used for visible applicationsdue to non-uniform appearance. A typical hot melt sealant compositionutilizes polyolefins that can be difficult to paint and which have pooradhesion to non-porous metallic surfaces, such as steel and aluminum.

Recently there has been a trend towards more “user-friendly” polyvinylchloride-based sealants that are provided in the form of a rope or atape because the handling properties of these materials permit fasterinstallation and eliminate the need to finesse the material afterapplication. Other materials have also been supplied as a strip or atape.

Once the sealant has been applied, its exposed surface may be coveredwith a plastic or rubber molding having a flexible top surface, whichmolding may be painted, for example to match or complement the color ofthe vehicle exterior. Alternatively, a metal molding may be used. Themolding is typically attached to the sealant surface using a mechanicalfastener or a pressure sensitive adhesive.

During its life the motor vehicle may be exposed to very coldtemperatures of −20° C. or lower, for example, −30 to −40° C.,especially if the vehicle is destined for use in extreme northernclimates. Under such conditions, sealants, particularly those that maybe used in roof ditch applications, should desirably maintain much ofthe flexibility that they demonstrate under more ordinary temperatures.This will help prevent the sealant from cracking, breaking, delaminatingor lifting up from the surface to which it has been applied as a resultof stresses caused by ordinary vehicle use. This not only permits theintrusion of dirt, moisture, and other undesirable materials but cancause a subsequently applied molding to become loose.

SUMMARY OF THE INVENTION

In general, this invention relates to compositions for sealingdiscontinuities and to articles used in sealing the discontinuities, aswell as to methods of sealing the discontinuities. The sealantcompositions of the invention are especially useful for sealing thetypes of discontinuities typically found in motor vehicles such as anoverlap seam or joint, a butt seam or joint, a depression orindentation, a hole, a spot weld, or a manufacturing defect. The sealsare effective in preventing water, dirt, snow, and other undesirablematerials from entering the discontinuity and causing corrosion. Quiteadvantageously, sealant compositions according to the invention haveexcellent flexibility, even after conditioning at a temperature of −20°C.

Accordingly, and in one embodiment, the invention is directed to acomposition comprising a curable epoxy-containing material, a firstthermoplastic polyurethane component, a curative for theepoxy-containing material, and, optionally, a second thermoplasticpolyurethane component that is different than the first thermoplasticpolyurethane component. The epoxy-containing material and thermoplasticpolyurethane component(s) when melt-blended, but still uncured, displayonly a single phase. After curing the sealant composition isphase-separated. In addition, the composition passes the test for “LowTemperature Flexibility” that is described more fully hereinbelow.

The thermoplastic polyurethane component is preferably based on apolyether polyol, more preferably, a polytetramethylene oxide polyol.Thus, in another embodiment, the invention relates to a composition thatcomprises a curable epoxy-containing material, a first thermoplasticpolyurethane component that is the polymerization product of apolymerizable mixture comprising a polyisocyanate and apolytetramethylene oxide polyol, a curative for the epoxy-containingmaterial, and optionally, a second thermoplastic polyurethane componentthat is different than the first thermoplastic polyurethane component.Such compositions provide a melt-flowable sealant for sealingdiscontinuities in the surface of a substrate, such as those found inmotor vehicles.

In certain embodiments the polytetramethylene oxide polyol preferablyhas a number average molecular weight of at least 600, especially whenused in combination with an aliphatic polyisocyanate. In otherembodiments, the polytetramethylene oxide polyol preferably has a numberaverage molecular weight of at least 1000, especially when used incombination with an aromatic polyisocyanate. Diisocyanates are preferredfor use as the polyisocyanate. Thus, the polymerizable mixture for firstthermoplastic polyurethane component preferably comprises either analiphatic diisocyanate, a polytetramethylene oxide polyol that has anumber average molecular weight of at least 600, and a diol chainextending agent, or an aromatic diisocyanate, a polytetramethylene oxidepolyol that has a number average molecular weight of at least 1000, anda diol chain extending agent.

The compositions of the invention are preferably tacky at a temperatureof about 15 to 25° C. In addition, it is preferred that they display atleast one glass transition temperature of less than −20° C., morepreferably, less than −30° C., even more preferably less than 40° C.,and most preferably −40 to −50° C. The compositions of the inventionfurther and preferably have a Shore D hardness of less than 50 or aShore A hardness of less than 85.

The compositions of the invention generally include about 20 to 70weight percent (wt. %) of the epoxy-containing material, and about 30 to80 wt. % of any thermoplastic polyurethane component present in thecomposition, wherein the sum of these materials is 100 wt. %.Preferably, however, the sealant compositions include about 20 to 40 wt.% of the epoxy-containing material, and about 60 to 80 wt. % of anythermoplastic polyurethane component present in the composition. Morepreferably, the sealant compositions comprise about 20 to 38 wt. %epoxy-containing material, and 62 to 80 wt. % thermoplastic polyurethanecomponent. Even more preferably, the sealant compositions comprise about25 to 35 wt. % epoxy-containing material, and 65 to 75 wt. %thermoplastic polyurethane component. Most preferably, the sealantcompositions comprise about 30 to 33 wt. % epoxy-containing material,and 67 to 70 wt. % thermoplastic polyurethane component.

The sealant compositions may further comprise a second thermoplasticpolyurethane component, which preferably is the polymerization productof a polymerizable mixture comprising a polyisocyanate and a polyesterpolyol. Other materials typically found in the sealant compositionsinclude a thermally activated curative, for example, dicyandiamide, andan accelerator such as an imidazole. The sealant compositions may alsoinclude a hydroxyl- or carboxyl-terminated polyester compound.Preferably such materials are semi-crystalline at room temperature witha softening point of less than about 140° C., and a number averagemolecular weight of about 7,500 to 200,000.

Various sealant articles may also be readily provided by combining alayer of a sealant composition according to the invention with anotherlayer that is attached thereto such as a dimensionally stablethermoplastic film or a B-staged, thermosetting plastic cap, thoughother layers may be used too.

The invention also relates to a method of sealing a discontinuity in thesurface of a substrate. This method comprises the steps of:

a) placing over the discontinuity, a sealant composition according tothe invention,

b) heating the sealant composition to cause the composition to flow andseal the discontinuity; and

c) allowing the sealant composition to cool.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully appreciated with reference to thefollowing drawings in which:

FIG. 1 is a perspective view of one embodiment of a sealant articleaccording to the invention; and

FIG. 2 is a cross-sectional view taken along lines 2—2 in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention pertains to a composition that can be used to form aprotective seal over a discontinuity such as an overlap seam or joint, abutt seam or joint, a depression or indentation, a hole, a spot weld, ora manufacturing defect so as to prevent, water, dirt, snow, and otherundesirable materials from entering the discontinuity and causingcorrosion. The sealant composition is preferably solid at roomtemperature. A slight amount of tackiness at or slightly below roomtemperature is desirable for helping to initially position the sealant(or an article containing the sealant) over a joint or a seam, such asda motor vehicle roof ditch. However, sealant compositions that aresubstantially tack-free at room temperature are also contemplated.

The sealant compositions may be regarded as melt-flowable. That is, whenplaced over the joint and heated, the sealant composition first softensand conforms to the surface of the discontinuity, thereby pushing outtrapped air. Further into the heating cycle, as the composition becomeshotter, it becomes tacky, and bonds to the surface. The sealantcomposition is thermosetting such that it cures (i.e., covalentlycrosslinks) upon heating and resists flowing following cooling andre-heating.

The sealant compositions of the invention, once cured, exhibit excellentflexibility at low temperatures and, as described more fullyhereinbelow, can be easily bent about a mandrel without cracking orbreaking, even after conditioning at a temperature of −30° C. It is alsopreferred that the cured sealant composition possess at least 10%elongation when tested at −20° C.

The sealant compositions of the invention comprise, and more preferablyconsist essentially of, an epoxy-containing material, a thermoplasticpolyurethane component, and a curative for the epoxy-containingmaterial. The epoxy-containing material contributes to the ultimatestrength and heat resistance of the sealant composition, while thethermoplastic polyurethane component provides conformability, pliabilityand flexibility, especially at low temperatures. The curative permitsthe composition to cure. Preferably, the curative is thermally-activatedsuch that the composition cures upon exposure to an appropriate heatsource for an appropriate period of time.

Useful epoxy-containing materials are epoxy resins that have at leastone oxirane ring polymerizable by a ring opening reaction. Suchmaterials, broadly called epoxides, include both monomeric and polymericepoxides and can be aliphatic, cycloaliphatic, or aromatic. Thesematerials generally have, on the average, at least two epoxy groups permolecule preferably more than two epoxy groups per molecule. Suchmaterials may be referred to as polyepoxides and includeepoxy-containing materials in which the epoxy functionality is slightlyless than 2, for example, 1.8. The “average” number of epoxy groups permolecule is defined as the number of epoxy groups in theepoxy-containing material divided by the total number of epoxy moleculespresent. The polymeric epoxides include linear polymers having terminalepoxy groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol),polymers having skeletal oxirane units (e.g., polybutadienepolyepoxide), and polymers having pendent epoxy groups (e.g., a glycidylmethacrylate polymer or copolymer). The molecular weight of theepoxy-containing material may vary from 58 to about 100,000 or more.Mixtures of various epoxy-containing materials can also be used.

Useful epoxy-containing materials include those which containcyclohexene oxide groups such as the epoxycyclohexanecarboxylates,typified by 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate,3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate,and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate. For a more detailedlist of useful epoxides of this nature, reference may be made to U.S.Pat. No. 3,117,099.

Further epoxy-containing materials which are particularly useful areglycidyl ether monomers such as glycidyl ethers of polyhydric phenolsobtained by reacting a polyhydric phenol with an excess of chlorohydrinsuch as epichlorohydrin (e.g., the diglycidyl ether of2,2-bis-(2,3-epoxypropoxyphenol) propane). Further examples of epoxidesof this type which can be used in the practice of this invention aredescribed in U.S. Pat. No. 3,018,262. Other useful glycidyl ether basedepoxy-containing materials are described in U.S. Pat. No. 5,407,978.

There are a number of commercially available epoxy-containing materialswhich can be used. In particular, epoxides which are readily availableinclude octadecylene oxide, epichlorohydrin, styrene oxide,vinylcyclohexene oxide, glycidol, glycidyl methacrylate, diglycidylether of Bisphenol A (e.g., those available under the trade designationsEPIKOTE 828, EPIKOTE 1004, and EPIKOTE 1001F from Shell Chemical Co.,and DER-332 and DER-334, from Dow Chemical Co.), diglycidyl ether ofBisphenol F (e.g., ARALDITE GY281 from Ciba-Geigy Corp.),vinylcyclohexene dioxide (e.g., ERL 4206 from Union Carbide Corp.),3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexenecarboxylate (e.g.,ERL-4221 from Union Carbide Corp.),2-(3,4-epoxycylohexyl-5,5-spiro-3,4-epoxy)cyclohexane-metadioxane (e.g.,ERL-4234 from Union Carbide Corp.), bis(3,4-epoxycyclohexyl)adipate(e.g., ERL-4299 from Union Carbide Corp.), dipentene dioxide (e.g.,ERL-4269 from Union Carbide Corp.), epoxidized polybutadiene (e.g.,OXIRON 2001 from FMC Corp.), epoxy silanes (e.g.,beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane andgamma-glycidoxypropyltrimethoxy-silane, commercially available fromUnion Carbide), flame retardant epoxy resins (e.g., DER-542, abrominated bisphenol type epoxy resin available from Dow Chemical Co.),1,4-butanediol diglycidyl ether (e.g., ARALDITE RD-2 from Ciba-GeigyCorp.), hydrogenated bisphenol A-epichlorohydrin based epoxy resins(e.g., EPONEX 1510 from Shell Chemical Co.), and polyglycidyl ether ofphenolformaldehyde novolac (e.g., DEN-431 and DEN-438 from Dow ChemicalCo.). Blends of different epoxies may also be used.

Preferred epoxy-containing materials may also be selected based on theirreactivity and viscosity. As the reactivity of the epoxy-containingmaterial increases, the resulting sealant composition will flow lessupon heating, which could result in poor wetting of the substratesurface surrounding the discontinuity and/or incomplete sealing of thediscontinuity. As the reactivity of the epoxy-containing materialdecreases, however, the sealant composition may flow too much uponheating and/or may not completely cure. The viscosity of theepoxy-containing material can also influence the melt flow properties ofthe sealant composition. In general, a low viscosity epoxy resin isdesired as it can be more easily processed at lower temperatures whichhelps to avoid premature activation of any thermally-activated curativethat may be included in the sealant composition. In turn, this canextend the storage life of the composition.

The compositions of the invention also include a thermoplasticpolyurethane component. A thermoplastic polyurethane component refers toa polymeric material containing urethane moieties,

which material possesses thermoplastic processing characteristics. Thatis, the material softens and flows upon heating so that it can beshaped, and then hardened upon cooling. Upon reheating, the materialbecomes soft again. The thermoplastic polyurethane component is selectedso as to achieve the desired miscibility with the epoxy-containingmaterial (as well as other sealant composition ingredients that do notpromote curing of the epoxy-containing material). The thermoplasticpolyurethane component also contributes to the excellent low temperatureproperties of the sealant composition.

Desired thermoplastic polyurethane components form a homogeneous, singlephase mixture when blended in the melt phase with the epoxy-containingmaterial (i.e, melt-blended) but without curing the epoxy-containingmaterials. The formation of a homogeneous, single phase mixture isevidenced by the mixture being clear when melt-blended Upon curing ofthe epoxy-containing material, however, a multi-phase or phase-separatedcomposition results, one phase being attributable to the curedepoxy-containing material and another phase resulting from thethermoplastic polyurethane component. The presence of a phase-separatedcomposition can be shown by the presence of multiple Tan δ (delta) peaksin a dynamic mechanical thermal analysis (DMTA) of the curedcomposition, as described more fully below.

Preferred thermoplastic polyurethane components for use in the inventionhave at least one glass transition temperature (Tg) of less than −20°C., more preferably less than −30° C., even more preferably less than40° C., and most preferably in the range of −50 to −40° C. As a result,the sealant compositions of the invention, once cured, display glasstransition temperatures in the same ranges. The glass transitiontemperature for the thermoplastic polyurethane component or the curedsealant composition can be measured as the temperature at which the Tanδ peak attributable to the thermoplastic polyurethane component occursin a DMTA assessment, which peak should have an amplitude of at least0.05 unit.

Preferred thermoplastic polyurethane components for use in the inventionalso have a hardness value of less than 50 when measured on the Shore Dscale or less than 85 when measured on the Shore A scale using the testmethod described in ISO 868: 1985, Plastic and ebonite determination ofindentation hardness by means of a durometer (Shore hardness). Selectingthermoplastic polyurethane components having hardness values in theseranges also provides sealant compositions that are easier to mix atlower temperatures.

With these considerations in mind, thermoplastic polyurethane componentsuseful in the invention are obtained as the polymerization product of apolymerizable mixture comprising a polyisocyanate and a polyetherpolyol. Preferably the resulting thermoplastic polyurethane component issubstantially linear in nature.

The term polyisocyanate also includes isocyanate-terminated prepolymers.The polyisocyanates used to form the thermoplastic polyurethanecomponent may be linear or branched, aliphatic, cycloaliphatic,araliphatic, heterocyclic or aromatic, or any combination of suchpolyisocyanates. Aliphatic polyisocyanates are preferred when a sealantcomposition that is tacky at room temperature is desired or if it isimportant to provide a thermoplastic polyurethane component that has alower viscosity or that can be melt processed at lower temperatures(e.g., less than 90° C.) so as to avoid premature activation of anythermally-activated curative.

Particularly suitable polyisocyanates correspond to the formulaQ(NCO)_(n) wherein n is an integer of from about 2 to about 4, mostpreferably about 2 so as to yield diisocyanates. An isocyanatefunctionality of 2.2 or less, more preferably 2.15 or less, and mostpreferably in the range of 2.0 to 2.1 promotes the formation of athermoplastic polyurethane component, as opposed to a polyurethanematerial that would be considered thermosetting. Q is selected fromaliphatic hydrocarbon radicals containing from about 2 to about 100carbon atoms. Q may include cycloaliphatic hydrocarbon radicals,aromatic hydrocarbon radicals or heterocyclic aromatic radicals andaraliphatic hydrocarbon radicals. Portions of Q may contain heteroatomsincluding oxygen, nitrogen, sulfur and halogens.

Examples of polyisocyanates that may be used include ethylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylenediisocyanate, trimethylhexamethylene diisocyanate, 1,12-dodecanediisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3 and1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 2,4- and 2,6-hexahydrotolylene diisocyanate, hexahydro-1,3and -1,4-phenylene diisocyanate, hexahydro-2,4′- and4,4′-diphenylmethane diisocyanate, 1,3-and 1,4-phenylene diisocyanate,2,4- and 2,6-tolylene diisocyanate, diphenylmethane2,4′- and4,4′-diisocyanate, and naphthylene-1,5-diisocyanate. Mixtures ofdifferent isocyanates may also be used.

Preferred polyisocyanates include hexamethylene diisocyanate, theisocyanurate and the biuret thereof,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (isophoronediisocyanate), the tolylene diisocyanates and isocyanurates thereof, themixed isocyanurate of tolylene diisocyanate and hexamethylenediisocyanate, 4,4′-methylene-bis(cyclohexyl diisocyanate), and thediphenylmethane diisocyanates.

Polyether polyols useful in the practice of the invention are typicallysubstantially linear compounds corresponding to the general structuralformula HO—D—OH and having a hydroxyl functionality of about 2.2 orless, preferably about 2.0, wherein D represents the organic residue ofa polyether linkage. A thermoplastic polyurethane component of desiredcharacteristics may be obtained by employing polyether polyols having anumber average molecular weight of at least 600 in the case of analiphatic thermoplastic polyurethane component, or at least 1000 in thecase of an aromatic thermoplastic polyurethane component. Most preferredare polyether polyols, which in addition to displaying the propertiesdescribed above, are polytetramethlyene oxide polyols, which can beobtained from a cationic ring-opening polymerization of tetrahydrofuran.Examples of commercially useful polytetramethylene oxide polyols includethe POLYMEG series from QO Chemicals, Inc. (e.g., POLYMEG 650, 1000 and2000), the TERATHANE series from E.I. duPont de Nemours and Company(e.g., TERATHANE 650, 1000 and 2000), POLYTHF from BASF Corp., andcombinations or mixtures thereof

The polymerization mixture from which the thermoplastic polyurethanecomponent is obtained may also include a chain extending agent toproduce a thermoplastic polyurethane component of higher molecularweight. Chain extending agents, compounds which carry at least twoactive hydrogen atoms per molecule, preferably have a molecular weightof from about 52 to below 500, most preferably from about 62 to about250. Examples of useful chain extending agents are the following:ethylene glycol, propane-1,2-diol, butane-1,4-diol; hexane-1,6-diol;2-ethyl-1,6-hexanediol; dihydroxyethylurea; terephthalicacid-bis(β-hydroxyethylamide); hydroquinone-bis-hydroxy-ethyl ether;naphthylene-1,5-bis-hydroxyethyl ether;1,1-dimethyl-4-(bis-β-hydroxyethyl)-semicarbazide; succinic acid;-adipicacid; isophthalic acid; 1,4-cyclohexanedicarboxylic acid,ethylenediamine; hexamethylenediamine; 1,4-cyclohexanediamine;hexahydro-m-xylene diamine; m-xylylene diamine; p-xylylene diamine;bis(β-aminoethyl)-oxalamide; piperazine; 2, -dimethylpiperazine;ethanolamine; 6-aminocaproic acid; 4,4-diaminodiphenylmethane;4,4′-diaminodiphenyldimethylmethane, 2-aminoacetic acid hydrazide;4-aminobutyric acid hydrazide; 6-aminocaproic acid hydrazide;2-hydroxy-acetic acid hydrazide; 2-aminobutyric acid hydrazide;6-hydroxycaproic acid hydrazide; carbodihydrazide; hydracrylic aciddihydrazide; adipic acid dihydrazide; isophthalic acid dihydrazide;,m-xylylene dicarboxylic acid dihydrazide; ethylene glycol-bis-cabazinicester; butanediol-bis-semicarbazide andhyexamethylene-bis-semicarbazide.

The use of diamine chain extenders results in the formation ofpolyurethane/urea materials. At low levels of such chain extenders, theformation of polyurethane segments predominates and the resultingmaterials may still be regarded as a thermoplastic polyurethanecomponent for use in the invention.

The polymerization mixture for the thermoplastic polyurethane componenttypically has an isocyanate (NCO) index of about 0.95 to 1.05, morepreferably about 1.0 so as to promote the formation of a thermoplasticmaterial rather than a thermosetting polyurethane. The isocyanate indexrefers to the molar ratio of isocyanate groups to hydroxyl groups in thepolymerizable mixture.

A variety of thermoplastic polyurethane components are commerciallyavailable and may be used in the practice of the invention, including,for example, TEXIN DP7-3005 from Bayer Corporation, DESMOPAN KU2-8600from Bayer Corporation, and the MORTHANE PE series from Morton ChemicalCompany (e.g., 192-100, 193-100 and 299-100).

The sealant compositions of the invention include a curative for curingthe epoxy-containing material. Preferably, the curative is thermallyactivated so as to effect curing or hardening of the epoxy-containingmaterial under the influence of heat. For example, useful thermallyactivated curatives include amine, amide, imidazole, Lewis acid complex,and anhydride type materials. The curative may be of any type, butpreferably is an amine type hardener that is selected from the groupcomprising dicyandiamide, imidazoles, polyamine salts and combinationsthereof Acid-based curatives are less preferred. Amine-type hardenersare available from a variety of sources, e.g., OMICURE™, available fromOmicron Chemical, AJICURE™, available from Ajinomoto Chemical, andAmicure™ CG 1200 available from Air Products.

In certain cases, it may be advantageous to add an accelerator to thesealant composition, so that it will fully cure at a lower temperature,or will fully cure when exposed to heat for shorter periods of time.Imidazoles are useful, suitable examples of which include2,4-diamino-6-(2′-methyl-imidazoyl)-ethyl-s-triazine isocyanurate;2-phenyl-4-benzyl-5-hydoxymethylimidazole; and Ni-imidazole-phthalate.CUREZOL 2-MZ azine, available from Air Products, is one example of auseful, commercially available material.

The activation temperature for the thermally-activated curative isselected so as to avoid premature curing of the epoxy-containingmaterial under normal storage and handling temperatures for the sealantcomposition, as well as during the preparation and application of thesealant, which typically involve temperatures of up to about 105° C. Onthe other hand, if the activation temperature is too high, largeramounts of heat will be required to cure the sealant composition. Thus,it is preferred that the curative be selected so as to permit thesealant composition to fully cure in a time of about 15 to 60 minutes.(By “fully cure” it is meant that the sealant composition curessufficiently for use in the intended application.) Curatives that havean activation temperature of about 140 to 180° C., more preferably about160 to 170° C. are desired.

As described herein, there are particular advantages associated with asealant composition that incorporates a thermoplastic polyurethanecomponent based on a polyether polyol. In some instances, however, theperformance of the sealant composition may be beneficially influenced byalso including a thermoplastic polyurethane component based on apolyester polyol. For example, this thermoplastic polyurethane componentmay be selected to lower the viscosity or the melting temperature of thesealant composition (relative to sealant compositions that do notinclude this ingredient). This is especially the case if thethermoplastic polyurethane component based on the polyester polyoldisplays a higher glass. transition temperature than the polyetherpolyol based thermoplastic polyurethane component that is also includedin the sealant composition. Thermoplastic polyurethane components basedon polyester polyols preferably display a softening point of lower than60° C., and more preferably lower than 50° C. (as measured according toASTM D 816).

The amount of thermoplastic polyurethane component based on a polyesterpolyol comprises up to about 40 wt. % of the total thermoplasticpolyurethane components in the sealant composition, more preferably upto about 30 wt. %.

Such thermoplastic polyurethane components are similar in composition tothe thermoplastic polyurethane components previously described exceptthat the polyether polyol is replaced by a polyester polyol. Polyesterpolyols useful in the practice of the invention are typicallysubstantially linear compounds corresponding to the general structuralformula HO—E—OH and having a hydroxyl functionality of about 2.2 orless, preferably about 2.0, wherein E represents the organic residue ofa polyester linkage. Alternatively, the polyester polyol may be carboxylterminated.

Polyester components useful for forming such thermoplastic polyurethanecomponents comprise the reaction product of dicarboxylic acids (or,their diester equivalents, including anhydrides) and diols. The diacids(or diester equivalents) can be saturated aliphatic acids containingfrom 4 to 12 carbon atoms (including branched, unbranched, or cyclicmaterials having 5 to 6 carbon atoms in a ring) and/or aromatic acidscontaining from 8 to 15 carbon atoms. Examples of suitable aliphaticacids are succinic, glutaric, adipic, pimelic, suberic, azelaic,sebacic, 1,12-dodecanedioic, 1,4-cyclohexanedicarboxylic,1,3-cyclopentanedicarboxylic, 2-methylsuccinic, 2-methylpentanedioic,3-methylhexanedioic acids, and the like. Suitable aromatic acids includeterephthalic acid, isophthalic acid, phthalic acid,. 4,4′-benzophenonedicarboxylic acid, 4,4′-diphenylmethanedicarboxylic acid,4,4′-diphenylthioether dicarboxylic acid, and 4,4′-diphenylaminedicarboxylic acid. Preferably the structure between the two carboxylgroups in the diacids contains only carbon and hydrogen, and morepreferably, the structure is a phenylene group. Blends of the foregoingdiacids may be used.

The diols include branched, unbranched, and cyclic aliphatic diolshaving from 2 to 12 carbon atoms. Examples of suitable diols includeethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol,1,4-butanediol, 1,3-butanediol, 1,5-pentanediol,2-methyl-214-pentanediol, 1,6-hexanediol,cyclobutane-1,3-di(2′-ethanol), cyclohexane-1,4-dimethanol,1,0-decanediol, 1,12-dodecanediol, and neopentyl glycol. Long chaindiols including poly(oxyalkylene)glycols in which the alkylene groupcontains from 2 to 9 carbon atoms, preferably 2 to 4 carbon atoms, mayalso be used. Blends of the foregoing diols may be used.

Examples of useful, commercially available thermoplastic polyurethanecomponents based on polyester polyol include DESMOCOLL 406 and DESMOCOLL500 from Bayer Corporation.

It is also possible for the thermoplastic polyurethane component toinclude polymerized units derived from both polyether polyol andpolyester polyol.

In other embodiments, the sealant compositions may include a hydroxyl-or carboxyl-terminated polyester compound in addition to theepoxy-containing material and the thermoplastic polyurethane component.Such polyester compounds can be useful for lowering the viscosity or themelting temperature of the sealant composition (relative to sealantcompositions that do not include this ingredient). Preferred polyestercompounds are semi-crystalline at room temperature (i.e., they display acrystalline melting point as determined by differential scanningcalorimetry, preferably with a maximum melting point of about 200° C.).The preferred polyester compounds have a softening point of less thanabout 140° C., more preferably less than about 110° C. In addition, thepreferred materials are solid at room temperature with a number averagemolecular weight of about 7500 to 200,000, more preferably about 10,000to 50,000, and most preferably about 15,000 to 30,000. The polyestercompound may be provided by the various polyester polyols discussed inconjunction with the polyester-based thermoplastic polyurethanecomponents. These materials are typically employed in an amount of about20 to 80 wt. % based on the weight of said thermoplastic polyurethaneand can be beneficially employed in combination with thermoplasticpolyurethane components that have a molding temperature in the range ofabout 140 to 200° C. Dynapol™ S1402 (softening point of 92° C.) fromHüls America, Inc., is one example of a useful, commercially availablepolyester compound.

Additionally, and optionally, up to 50% of the total volume of thecomposition, may be provided by various fillers, adjuvants, additivesand the like such as silanes; chelating agents; processing aids; flameretardants; polymeric additives plasticizers; UV absorbents; surfaceactive agents calcium carbonate, silica, glass; clay; talc; pigments,colorants; glass, ceramic or polymeric beads or bubbles; glass,polymeric or ceramic fibers; antioxidants; and the like so as to reducethe weight or cost of the composition, adjust viscosity, and provideadditional reinforcement but without materially adversely affecting theperformance of the sealant composition.

The individual ingredients for the sealant composition are combined inrelative amounts that are determined by the nature of the ingredientsand the properties desired in the ultimate sealant composition. Forexample, as the amount of epoxy-containing material increases theresulting sealant composition becomes less flexible and less tacky, theamount of flow that occurs upon heating the composition during thesealing process increases, and the propensity of the sealant to resistcracking and breaking when stressed under low temperature conditions isreduced. On the other hand, as the amount of epoxy-containing materialdecreases, the sealant composition may not flow adequately to wet-outthe substrate surface surrounding the discontinuity and to seal thediscontinuity.

Within these parameters, the sealant compositions of the invention maybroadly incorporate about 20 to 70 weight per cent (wt. %)epoxy-containing material, and 30 to 80 wt. % thermoplastic polyurethanecomponent, based on these ingredients providing a combined amount of 100wt. %. Preferably, however, the sealant compositions comprise about 20to 40 wt. % epoxy-containing material, and 60 to 80 wt. % thermoplasticpolyurethane component. More preferably, the sealant compositionscomprise about 20 to 38 wt. % epoxy-containing material, and 62 to 80wt. % thermoplastic polyurethane component. Even more preferably, thesealant compositions comprise about 25 to 35 wt. % epoxy-containingmaterial, and 65 to 75 wt. % thermoplastic polyurethane component. Mostpreferably, the sealant compositions comprise about 30 to 33 wt. %epoxy-containing material, and 67 to 70 wt. % thermoplastic polyurethanecomponent.

Any curative for the epoxy-containing material and any accelerator forthe epoxy curing reaction are employed in an effective amount, that is,an amount sufficient to fully cure the epoxy-containing material in viewof the time for and the temperature to which the sealant composition isheated to effect curing. The sealant is fully cured when it is curedsufficiently for use in the intended application, for example, iteffectively seals a discontinuity in a motor vehicle from water, snow,dirt and other undesirable materials under the ordinary conditions ofuse. Within these guidelines, the curative is typically employed in anamount of about 1 to 15%, preferably about 2.5 to 4.5% based on the massof the composition. An accelerator is typically employed in an amount of0 to 2%, more preferably 0.2 to 0.7%. A typical curing cycle involvesheating the sealant composition at a temperature of about 140 to 180° C.for about 15 to 60 minutes.

Sealant compositions according to the invention may be readily prepared.The various ingredients (except those that promote curing of theepoxy-containing material such as curatives and accelerators) arecombined in a suitable mixing vessel, with the use of heat (typically toabout 140 to 180° C.) and agitation as necessary. Thus, the mixingvessel may range from a metal container in which the ingredients areheated locally and mixed by hand, to a batch mixer, to a single or twinscrew extruder having different mixing zones and in which thetemperature within each zone may be independently controlled. Theseingredients are thoroughly mixed and then cooled to a temperature belowthe activation temperature for any subsequently added thermallyactivated curative. The curative may be added at this time, along withany accelerator for the curing reaction, with thorough mixing.

The sealant composition may then be formed into any desired shape,depending upon the ultimate use for the sealant. For example, thesealant composition may be supplied in the form of a sealant film bycoating or extruding the composition onto a single removable liner orbetween a pair of removable liners, cooling the applied material toambient temperature, and then, if necessary, cutting the resultingsealant film to the desired shape. The composition may be coated with aheated knife coater or other coating apparatus or extruded through a diehaving the desired profile. The removable liners may be provided by anyof those conventionally used in the preparation of adhesive or sealantfilms and often comprise a polymeric film (e.g., polyethyleneterephthalate) that has been treated with a release agent such as asilicone or fluorosilicone polymer.

Although the sealant composition has been described as a single layerconstruction, two or more melt-flowable sealant layers having differentmelt flow properties may be laminated together to form the sealantcomposition. For example, the top layer can be formulated to havegreater flow properties than the bottom layer, while the bottom layer isformulated to have higher strength for better handling properties. Onelayer may be formulated to be more tacky or to have higher strength inthe uncured state than an adjacent layer.

Other layers may be combined with the sealant layer so as to form asealant article. Such layers include a pressure-sensitive adhesive layerwhich may be thermosettable or not, a layer capable of cross-linkingwith the sealant layer at the interface between two adjacent layers, awoven or nonwoven web or scrim, a thermoplastic film, or a metal orplastic cap. The sealant article may include one or more of theselayers.

The thermoplastic film is preferably dimensionally stable attemperatures to which the film might be exposed when applying thesealant composition to a substrate (e.g., when the sealant compositionis heated to a temperature necessary to cause melt flow and/or curing),or after the sealant has been applied (e.g., exposure to cold weathertemperatures, sunlight, etc.). By dimensionally stable, it is meant thatthe thermoplastic film has sufficient integrity at the temperatures ofuse and application, and particularly during heat curing of the sealantcomposition at about 140° C. to 180° C. for 15 to 60 minutes, that itdoes not melt and flow. Also the films do not wrinkle when they areheated to the melt sealing temperature and subsequently cooled. Thefilms also have enough integrity to prevent entrapped air bubbles in thesealant layer from blowing through the film and causing a defect. Thefilms can be used to provide smooth surfaces for painting or as thefinished surface after the sealant article has been bonded to a surface.Films may be treated or primed to enhance paint adhesion. Preferredfilms include polyester films (e.g., polyethylene terephthalate) whichmay or may not be oriented, polyimide films, and polyolefin films (e.g.,ultrahigh molecular weight polyethylene, microporous ultrahigh molecularweight polyethylene, ultrahigh molecular weight polypropylene, andultrahigh molecular weight microporous polypropylene).

Alternatively, the sealant layer may be combined with a metal or plasticcap that provides an exposed outer surface that imparts decorative andaesthetic features to the surface to which the sealant article isapplied (e.g., the roof ditch of a motor vehicle). The shape of the capis selected based upon the particular discontinuity that the article isdesigned to seal. Such a cap is preferably designed to substantiallyretain its shape during the melt-sealing operation. A preferred materialfor the cap is a B-staged thermosetting composition such as a B-stagedepoxy-polyester blend. “B-staged” refers to an intermediate state in athermosetting resin reaction in which the material softens when heated,and swells, but does not dissolve in certain liquids.

A configuration that is particularly useful with seams or joints formedin the floor of recesses such as motor vehicle roof ditches is one inwhich the cross-sectional profile is characterized by a pair oflaterally extending, opposed extensions, at least one of which istapered in the thickness direction. Preferably, both of the opposedextension portions are tapered in the thickness direction. Arepresentative construction is illustrated in FIGS. 1 and 2 in which asealant article 10 comprises a sealant composition layer 12 and aplastic cap 14. The plastic cap includes a central body portion 16 and apair of laterally extending, opposed extensions 18 and 20 that taper inthe thickness direction and away from the central body portion. Thelength of sealant article 10 typically approximates the length of thediscontinuity to be sealed.

The additional layers may be mated with the sealant composition in avariety of ways. If the sealant composition and any additional layersare provided in the form of separate strips or tapes, then they may belaminated together using, for example, commercially available niprollers. If either or both of the additional layers and the sealantcomposition are tacky or pressure-sensitive, light pressure issufficient to bond the different components together. Preferably, atemporary, removable release liner is applied to the tacky surface toprotect it from contamination. In use, the tackiness of the sealantcomposition will provide sufficient adhesion to hold the components to asurface until the sealant article is cured and bonded permanently to thesurface.

If neither the additional layers nor the sealant composition are tacky,then the components can be bonded together by heating one or both of themating surfaces to a temperature at which at least one of the surfacesbecomes tacky enough to form a bond by applying light pressure.Alternatively, a tie layer can be used to adhere the two componentstogether. In use, a pressure-sensitive adhesive can optionally beapplied to part or all of the lower or bottom surface of the sealantcomposition to hold the article in place on the substrate until thesealant composition is fully cured.

Selected subsequent layers and the sealant composition can also be matedby coextruding the different materials to form a unitary tape or strip.

Alternatively, the sealant composition can be placed as a discreteelement on the surface to which a sealant article will be applied, andthe subsequent layers attached at a later time. For example, the sealantcomposition can be applied as a tape, or it can be pumped onto thesurface as a viscous liquid, paste or gel. Exposure to heat, e.g., froma paint bake oven cycle, will bond the subsequent layers to the sealantcomposition.

The above-described sealant compositions and articles are useful forsealing a variety of discontinuities such as overlap seams or joints,butt seams or joints, depressions or indentations, holes, spot welds,and manufacturing defects. They are particularly useful for sealingjoints formed in the floors of motor vehicle roof ditches. The sealantcomposition or article is first positioned over the discontinuity thatis to be sealed. Once the sealant has been secured over thediscontinuity it is then heated to a temperature sufficiently high tocause the sealant composition to undergo mass flow, cure and seal thediscontinuity, typically about 140 to 180° C. for 15 to 60 minutes.During the heating process, air in the region of the discontinuity isdisplaced by the melt flow of the sealant composition.

As noted elsewhere herein, the selection and amount of the sealantcomposition ingredients can influence the melt-flow characteristics ofthe sealant composition. It is desired that the sealant compositionexhibit sufficient flow upon heating that the substrate surfacesurrounding the discontinuity is wetted and that the discontinuity issealed, but without having the sealant flowing out of the area to besealed (for example, flow out of the roof ditch in a motor vehicle).Within these guidelines, a flow distance of about 20 to 60 mm under the“Melt Flow” test described below is desirable. In addition, for enhancedcommercial utility, it is desired that the melt flow of a sealantcomposition not decrease by more than 20%, even after extended (e.g., 3months) storage under ambient temperature conditions. Following heating,the entire assembly is cooled, resulting in a structure in which thesealant composition seals the discontinuity.

The invention will now be further described by way of the following testmethods and non-limiting examples.

TEST METHODS Test Methods for Uncured Sealant Compositions

Melt Flow

A steel test coupon measuring 23 cm×5 cm and 2 mm thick and bearing acoating of the primer ED 5100 (commercially available from AdvancedCoating Technology, Hillsdale, Mich., USA) was used as, received andprepared for the test by adhering a 12.5 mm wide strip of transfer tape(available as Tape 444 from 3M Company, St. Paul, Minn., USA) across theentire 5 cm width of the coupon and adjacent to one end of the coupon.

Then a 1 mm thick sample of uncured sealant composition measuring 14.5mm×25.4 mm was placed orthogonally to the transfer tape with one end ofthe sealant composition sample overlapping the transfer tape. Thesealant composition was applied by pressing onto the surface firmly byhand. The location of the end of the sealant composition that did notoverlap the transfer tape was marked on the coupon. The coupon bearingthe sealant composition was then placed at a 450 angle in a forced airoven at 177° C. for 20 min. The coupon edge bearing the transfer tapewas at a higher elevation.

The coupon was then removed from the oven and allowed to cool to ambienttemperature. The distance from the mark indicating the original edge ofthe sealant composition sample, to the edge of the sealant compositionafter melt flow had occurred was measured and recorded in mm. Twosamples were evaluated simultaneously and the results averaged.

180° Peel Adhesion from Stainless Steel

A sealant composition sample having a thickness of 1 mm and dimensionsof 2.54 cm wide by 20 cm long was rolled down two times on a stainlesssteel plate with a 6.8 kg rubber-coated rubber roller and allowed tostand 20 minutes before peel testing. Approximately 75 mm of the lengthof the sealant composition was bonded to the plate. Before applying thesealant composition sample, the stainless steel plate was wiped threetimes with methyl ethyl ketone and once with heptane. The peel adhesionwas measured using a tensile testing apparatus (Model Z030 from ZwickGmbH, Ulm, Germany) at a peel speed of 300 mn/min. One end of the testplate was grasped in one jaw of the tensile tester. The sample ofsealant composition was folded back at an angle of 180° and its free endgrasped in the second jaw of the tensile tester in the configurationcommonly utilized for 180° peel measurements. Three samples weremeasured and the results averaged. The results were measured in N/2.54cm.

Test Methods for Cured Sealant Compositions

Low Temperature Flexibility

A 1 mm thick sample of uncured sealant composition (50 mm×125 mm) wasadhered to a 0.385 mm thick stainless steel plate (50 mm×125 mm) by firmhand pressing and then rolling it down with a hand-held rubber-coatedroller using hand pressure to remove air bubbles. The sample was thenplaced in a forced air oven at 160° C. for 20 min. The cured sample wasthen allowed to equilibrate overnight to ambient conditions.

The cured sample was placed in a freezer having a temperature of −30° C.for 16 hours. The sample was then removed from the freezer and quicklybent over a 13 mm diameter mandrel (available as Mandrel Tester Model266 from Erichsen GmbH (Hemer-Sundwig, Germany)) which had also beencooled to −30° C. The back of the metal plate was placed on the mandreland the sample was bent backwards until a metal to metal angle of 45°was obtained.

The samples were then evaluated visually for cracks and fractures in thecured sealant composition. If no cracks were visible to the eye, thenthe sample was rated as “pass”. If cracks or fissures were present inthe cured sealant composition in the area which had been bent, then thesample was rated as “fail”.

Overlap Shear Strength from Abraded Aluminum

A 1 mm thick sample of a sealant composition in the form of a 20 mmdiameter disc was placed between two rectangular aluminum platesmeasuring 2 mm×25 mm×75 mm that had been abraded with a SCOTCHBRITE Pad#7447 available from 3M Company, washed with water, rinsed with a50%/50% by volume mixture of isopropyl alcohol and water, and thendried. Stainless steel spacers having a thickness of 0.8 mm were used tomaintain the bond thickness during curing.

The construction was held together in a heated press with a pressuresetting of 0.1-0.2 N/mm² and heated to 160° C. for 20 min. The sampleswere removed from the press and allowed to equilibrate at 23° C. and arelative humidity of 55% for 24 hours before testing.

One plate of the test construction was placed in the lower jaw of atensile tester (Model Z030 from Zwick GmbH, Ulm, Germany) and the otherplate was placed in the upper jaw. The jaws were then moved apart at aspeed of 5 mm/min until bond failure occurred. The maximum forcerequired to break the bond was recorded in N/mm² The test was performedthree times and the results averaged.

Overlap Shear Strength from Unabraded Aluminum

This overlap shear test was performed as described above, with theexception that the aluminum plates were neither abraded nor cleanedbefore use. (However, the plate surfaces were wiped with a paper tissuebefore applying the sealant composition.)

Water Resistance

A 1 mm thick uncured sample of sealant composition having the dimensionsof 50 mm×125 mm was placed on a steel test coupon (23 cm×5 cm) bearing acoating of the primer ED 5100 (commercially available from AdvancedCoating Technology, Hillsdale, Mich., USA) and rolled down with handpressure to remove air bubbles trapped in the bond line and cured at160° C. for 20 minutes

An X-shaped cut was made through the sealant composition to the steeltest coupon by cutting along the imaginary lines running betweenopposing corners of the plate. The scored samples were placed in water(deionized with 0.2% liquid dishwashing soap available commercially asPRIL from Henkel) at a temperature of 70° C. for a period of three days.The samples were removed, rinsed and dried in air.

The cross-cut area where the two cuts intersected was examined. Sampleswhere the sealant composition could be removed by hand from the platestarting at the cross-cut were rated as “fail” Samples where the sealantcomposition could not be removed by hand were rated as “pass”.

Simulated Roof Ditch Test

A 300 mm long section of motor vehicle roof ditch was simulated bybending two cold-rolled steel panels having a thickness of 1 mm into asquare u-shaped channel and spot welding them together in an overlappingconfiguration. The roof ditch had a width of 14.5 mm. The plates wereoverlapped in the bottom of the ditch to simulate a seam or a joint.

A section of uncured sealant composition having the dimensions of 1mm×295 mm×14 mm was placed on top of the overlapping area of the steelplates in the bottom of the simulated roof ditch and pressed down byhand. The test sample was then placed in a forced air oven at 160° C.for 20 min.

The sample was then evaluated visually, especially in the area of thespot welds, for bubble formation and the desired tendency of the sealantcomposition to flow into indentations in the ditch caused by the spotswelds. Adhesion to the roof ditch was evaluated by cutting the curedfilm with a razor blade.

Simulated Seam Sealing

A test substrate was prepared by attaching a 25 mm×150 mm×0.8 mm thickstrip of SPCC-SD steel (=cold-rolled steel panel, optionally with dullsurface finish) onto a 75 mm×150 mm×3 mm thick glass plate using adouble-sided pressure-sensitive adhesive tape. The step from the steeldown to the glass surface simulated a seam in the bottom of a roof ditchin a motor vehicle. A section of uncured sealant composition measuring20 mm×100 mm was placed over one edge of the steel strip and heated for10 minutes at 120° C. and then for 40 minutes at 140° C. After coolingto 23° C., the simulated seam (as represented by the step from the steelstrip down to the surface of the glass plate) was examined visuallythrough the glass to determine the quality of the seal that had formed.An acceptable seal was evidenced by the sealant composition havingmelted and flowed over the steel strip and filled the gap between thesurface of the glass plate and the steel strip.

The following qualitative descriptions were used to assess the seal thathad formed:

Good—an acceptable seal was formed along the entire 100 mm length of thesealant composition.

Fair—an acceptable seal was formed along the length of the sealantcomposition but with an unsealed air gap at one or both ends of thesealant composition.

Poor—unsealed air gaps were observed along the length of the sealantcomposition.

Temperature Cycle Aging Test

A 0.8 mm thick steel plate coated with an automotive grade electrondeposition coating (E-coating U-600 Black from Nippon Paint Co., Ltd.,Osaka, Japan) was bent into a square U-shaped channel measuring 25 mmlong×8 mm wide×3 mm deep to simulate a motor vehicle roof ditch.

A section of uncured sealant composition measuring 25 mm×7 mm was placedin the bottom of the simulated roof ditch channel and heated at 120° C.for 10 minutes. After cooling to room temperature, a standard automotivepaint primer (high molecular weight polyester based primer, crosslinkedwith melamine formaldehyde, obtained from Kansai Paint Co., Ltd., Osaka,Japan) was sprayed onto the sealant composition in a manner recommendedby the manufacturer and then cured at 140° C. for 20 minutes. Aftercooling to room temperature, an automotive base paint (high molecularweight polyester based primer, crosslinked with melamine formaldehyde,obtained from Kansai Paint Co., Ltd., Osaka, Japan) was sprayed over theprimer in a manner recommended by the manufacturer, cured at 140° C. for20 minutes, and then cooled to room temperature. The painted sealantcomposition was then exposed to a temperature cycle aging test. Onecycle consisted of 2 hours at −30° C., followed by 2 hours at roomtemperature (about 23° C.), and then 2 hours at 70° C. After 5 cycles,the condition of the sealant composition in the simulated roof ditchchannel was examined visually using the following qualitativedescriptions for the appearance.

Good—no difference in the visual appearance of the sealant compositionbefore and after the test.

Poor—the visual appearance of the sealant composition was deterioratedafter the test, as measured, for example, by the observation of a crackhaving formed between the edge of the sealant composition and theadjacent simulated roof ditch channel.

Cold Temperature Elongation

A section of uncured sealant composition was heated for 30 minutes at140° C. and then cooled to room temperature. A test specimen of thecured sample was then die cut into a No. 1 dumbbell shape according toJapan Industrial Standard (JIS) K-6251. The test specimen was thenmarked to show two parallel lines 40 mm apart from each other, The testspecimen was then clamped into the crosshead clamps (clamp distance isabout 60-70 mm) of a Tensilon Tester (manufactured by OrientecCorporation) fitted with a controlled temperature conditioning chamber.The clamped specimen was conditioned for 20 minutes at −20° C. in thechamber and then stretched at a crosshead speed of 50 mn/min until thespecimen broke. The elongation at break was calculated according to thefollowing formula

Elongation [%]=[(A−40)/40]×100

wherein A was the distance between the two parallel lines in mm when thespecimen broke. It was also noted if the sealant composition appearedbrittle.

250 Hour Water Soak

A sample was prepared by placing a strip of sealant compositionmeasuring 25 mm×40 mm on a 65 mm×150 mm E-coated steel panel, andheating for 10 minutes at 120° C. After cooling to room temperature, anautomotive paint primer was sprayed over the strip of sealantcomposition. The sample was cured for 20 minutes at 140° C. Aftercooling for at least 10 minutes, an automotive base paint was sprayedover the primer-coated sealant composition. The sample was cured for 20minutes at 140° C., and then cooled to room temperature. The E-coatedmetal panels, the paint primer, and the base paint that were used wereall as described in the Temperature Cycle Aging Test. The sample wassoaked in water at 40° C. for 250 hours and then visually examined withthe following qualitative descriptions of appearance:

Good—no different in the visual appearance of the sealant compositionbefore and after the test.

Poor—the visual appearance of the sealant composition was deterioratedafter the test as shown, for example, by wrinkles, blisters or bubblesthat had formed in the paint because water had penetrated the sealantcomposition.

Lap Joint Sealing

Two 0.8 mm thick E-coated metal plates like those used in theTemperature Cycle Aging Test described above were welded together toform a lap joint. A strip of uncured sealant composition measuring 20mm×100 mm was applied over the lap joint, heated for 10 minutes at 95°C., and then for 36 minutes at 140° C. After cooling, the sealantcomposition was examined visually to determine if the lap joint wassealed as indicated by the desired tendency of the sealant compositionto flow into the lap joint and adhere to the metal plates. A qualitativeevaluation of “Good” indicated that an acceptable seal was formed.

Surface Appearance

A simulated motor vehicle roof ditch was prepared by bending twoE-coated metal plates (like those described previously in theTemperature Cycle Aging Test) into a square-U-shaped channel and spotwelding them together in an overlapping configuration. The simulatedroof ditch measured 20 mm wide, 10 mm deep, and 300 mm long with thewelded seam or joint at the bottom of the ditch. Further, 10 recesses orindentations, each having a diameter of about 5 mm and a depth of about0.8 mm, were formed in the bottom of the ditch. A strip of uncuredsealant composition measuring 19 mm wide×300 mm long was placed in thebottom of the simulated roof ditch. The test specimen was then heatedfor 10 minutes at 100° C., followed by 20 minutes at 140° C., and thencooled for at least 10 minutes, and then heated again for 20 minutes at140° C. The simulated roof ditch was then visually examined, especiallyin the area of the indentations, for the desired tendency of the sealantcomposition to fill the indentations and to form a smooth flat surfacewithout depressions.

Other Test Methods

“Dynamic Mechanical Thermal Analysis (DMTA)”

A sealant composition was cured at 160° C. for 20 minutes. Circularsamples of the cured sealant composition having a thickness of about 1mm and a diameter of 7 mm were punched out and evaluated using a dynamicmechanical thermal analysis apparatus (Polymer Laboratories DMTA, ModelMK II, available from Rheometrics Scientific, Piscataway, N.J., USA).Plots of storage modulus (G′) versus temperature, loss modulus (G″)versus temperature, and Tan δ (delta) (G″/G′) versus temperature weremeasured between −100° C. and 200° C. using a heating rate of 2°C./min., a frequency of 1 Hz, and a strain of 1×16 microns.

DMTA can be used to measure the glass transition temperature of athermoplastic polyurethane component and the glass transitiontemperature of a cured sealant composition. The glass transitiontemperature for the cured sealant composition is measured as thetemperature at which the apex of the Tan δ peak attributable to thethermoplastic polyurethane component occurs, which peak should have anamplitude of at least 0.05 unit.

The presence of multiple Tan δ peaks in such an analysis indicates thatthe cured sealant composition has undergone the desired phase separationdescribed herein. Sealant compositions 1, 3, 4, 6, 8-10, 14, 15 and20-25 (described below) exhibited multiple Tan δ peaks indicative ofphase separation.

EXAMPLES

In the examples, all amounts given in “parts” refer to parts by weight.The examples include various abbreviations and trade names, which may beinterpreted according to the schedules shown below.

Schedules of Materials Used in the Examples

Thermoplastic Polyurethane Component

DESMOPAN KU2-8600 is a thermoplastic polyurethane (available from BayerCorp., Polymers Division, Pittsburgh, Pa., USA) having an aromaticpolyisocyanate/butanediol hard segment, and a polytetramethylene oxidesoft segment (soft segment molecular weight of approximately 1160), a Tgof −20° C., a Shore D hardness of 31, and a Shore A hardness of 82.

TEXIN DP7-3005 is a thermoplastic polyurethane (available from BayerCorp., Polymers Division, Pittsburgh, Pa., USA) having an aliphaticpolyisocyanate/butanediol hard segment and a polytetramethylene oxidesoft segment (soft segment molecular weight of approximately 1000), a Tgof −50 to 50° C. (plateau), a Shore D hardness of 43, and a Shore Ahardness of 83.

TEXIN DP7-3006 is a thermoplastic polyurethane (available from BayerCorp., Polymers Division, Pittsburgh, Pa., USA) having an aliphaticpolyisocyanate/butanediol hard segment, a polytetramethylene oxide softsegment (soft segment molecular weight of approximately 650), and aShore D hardness of 50.

TEXFN DP7-3007 is a thermoplastic polyurethane (available from BayerCorp., Polymers Division, Pittsburgh, Pa., USA) having an aliphaticpolyisocyanate/butanediol hard segment, a polyether soft segment, and aShore D hardness of 58.

MORTHANE PE 192-100 is a thermoplastic polyurethane (available fromMorton International Inc., Specialty Chemicals Division, Chicago, Ill.,USA) having an aliphatic polyisocyanate hard segment, a polyether softsegment, and a Shore A hardness of 76.

MORTHANE PE 193-100 is a thermoplastic polyurethane (available fromMorton International Inc., Specialty Chemicals Division, Chicago, Ill.,USA) having an aliphatic polyisocyanate hard segment, a polyether softsegment, and a Shore A hardness of 74.

MORTHANE PE 299-100 is a thermoplastic polyurethane (available fromMorton International Inc., Specialty Chemicals Division, Chicago, Ill.,USA) having an aliphatic polyisocyanate hard segment, a polyether softsegment, and a Shore A hardness of 75.

PEARLTHANE 125 is a thermoplastic polyurethane (available from MequinsaNorth America, Inc., Mohegan Lake, N.Y., USA) having an aromaticpolyisocyanate hard segment and a polyester soft segment, a Shore Ahardness of 85, and a Shore D hardness of 36.

PEARLTHANE 126 is a thermoplastic polyurethane (available from MequinsaNorth America, Inc., Mohegan Lake, N.Y., USA) having an aromaticpolyisocyanate hard segment and a polyester soft segment, a shore Ahardness of 92, and a Shore D hardness of 42.

MORTHANE PN 03 214 is a thermoplastic polyurethane (available fromMorton International Inc., Specialty Chemicals Division, Chicago, Ill.,USA) having an aliphatic polyisocyanate hard segment, a polyester softsegment, and a Shore A hardness of 92.

DESMOCOLL 406 is a thermoplastic polyurethane (available from Bayer.Corp., Polymers Division, Pittsburgh, Pa., USA) having an aromaticpolyisocyanate hard segment, a hydroxy polyester soft segment, asoftening point of approximately 40° C., and a Shore A hardness of 97.

DESMOCOLL 500 is a thermoplastic polyurethane (available from Bayer.Corp., Polymers Division, Pittsburgh, Pa., USA) having an aromaticpolyisocyanate hard segment, a hydroxy polyester soft segment, asoftening point of approximately 50° C., and a Shore A hardness of 97.

ET370 is a thermoplastic polyurethane (available from Takeda BadischeUrethane Industries, Ltd., Tokyo, Japan) with a polytetramethylene oxidesoft segment, a hard segment derived from butanediol and apolyisocyanate, and having a Shore A hardness of 70, and a moldingtemperature around 160° C.

ET880 is a thermoplastic polyurethane (available from Takeda BadischeUrethane Industries, Ltd., Tokyo, Japan) with a polytetramethylene oxidesoft segment, a hard segment derived from butanediol and apolyisocyanate, and having a Shore A hardness of 80, and a moldingtemperature around 190° C.

Epoxy-Containing Material

DEN 431 is an epoxy-novolac resin, available from Dow Chemical Co.,Midland, Mich., USA.

DEN 438 is an epoxy-novolac resin, available from Dow Chemical Co.Midland, Mich., USA.

EPIKOTE 828 is the diglycidyl ether of bisphenol A, available fromDeutsche Shell Chemie GmbH, Eschborn, Germany.

EPONEX DRH 1510 is a cycloaliphatic hydrogenated diglycidyl ether ofbisphenol A, available from Shell Nederland Chemie B.V., TheNetherlands.

EPIKOTE, 1001 is a diglycidyl ether of bisphenol A (epoxy equivalentweight of 525-550 g/eq), available from Yuka Shell Epoxy K.K., Tokyo,Japan.

EPIKOTE 1004K is a solid diglycidyl ether of bisphenol A (epoxyequivalent weight of 875-975 g/eq), available from Yuka Shell EpoxyK.K., Tokyo, Japan.

EPIKOTE 828 is a diglycidyl ether of bisphenol A (epoxy equivalentweight of 185-192 g/eq) available from Yuka Shell Epoxy K.K., Tokyo,Japan.

Epoxy Resin I is a bisphenol A endcapped aliphatic epoxy resin, asdescribed in Example 1 of U.S. Pat. No. 5,407,978 (Bymark et. al.).

Other Materials

A-187 refers to gamma-glycidyloxypropyltrimethoxysilane, available fromOSi Specialties of Danbury, Conn., USA.

H3636AS is a cyanoguanidine epoxy curing agent, available from AsahiDenka, Tokyo, Japan.

AEROSIL 200 is a hydrophilic fumed silica, available from Degussa Corp.of Ridgefield Park, N.J., USA.

AEROSIL R-972 is a hydrophobic fumed silica available from Degussa Corp.of Ridgefield Park, N.J., USA.

AMICURE CG1200 is dicyandiamide epoxy curing agent, available from AirProducts and Chemicals, Inc., Allentown, Pa., USA.

CUREZOL 2-MZ is an imidazole derivative epoxy curing accelerator,available from Air Products and Chemicals, Inc., Allentown, Pa., USA.

DYNAPOL S 1402 is a hydroxyl functional, semi-crystalline polyesterresin available from Hüls America (subsidiary of Hüls AG, Marl,Germany), with a melting point of 92° C., a glass transition temperatureof −12° C., and a melt flow rate at 160° C. of 120 g/10 minutes.

KRATON L1203 is an ethylene/butylene copolymer containing a singleterminal aliphatic primary hydroxy group on one end, available fromShell Chemical Co. of Houston, Tex., USA.

KRATON L2203 is an ethylene/butylene copolymer containing a terminalaliphatic primary hydroxy group on each end, available from ShellChemical Co. of Houston, Tex., USA.

2MZA is an imidazole derivate epoxy curing agent, available from ShikokuKasei Co. Ltd., Tokyo, Japan.

PET refers to polyethylene terephthalate.

TFA refers to 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, availablefrom Fluka Chemie AG, Buchs, Switzerland.

Sealant Compositions 1 to 30

Sealant compositions 1 to 30 were prepared according to the followingprocedure

The thermoplastic aliphatic or aromatic, respectively, polyurethanecomponent was combined with an epoxy-containing material, along with anyadditional components (other than curative or accelerator) in u metalcan. The mixture was, heated to 150° C. in case of an aliphaticpolyurethane component or 175° C. in case of an aromatic polyurethanecomponent, respectively, with intermittent hand-mixing for about threehours in case of an aliphatic polyurethane component or for about fourhours in case of an aromatic polyurethane component, respectively. Themixture was then allowed to cool to about 105° C. in case of analiphatic polyurethane component or 150° C. in case of an aromaticpolyurethane component, respectively, and then AMICURE CG 1200 curativeand CUREZOL 2-MZ accelerator were added and thoroughly mixed.

The mixture, having a temperature of about 100° C., was coated while hotbetween two 50 micron thick two silicone coated PET release liners usinga heated knife coater with a gap set to provide a 1 mm thick coating.The coating was allowed to cool to 23° C. under ambient conditions.

The specific composition of each sealant is summarized in Table 1. Theresulting film of sealant composition was cut to size and evaluatedusing the test methods described above with the result summarized in thevarious following tables.

TABLE 1 Thermoplastic Parts Parts Polyurethane Epoxy-ContainingDicyandi- Curezol 2- Polymeric Other Sealant Component Material amide MZAzine Silica Additive Materials Composition (parts) (parts) (parts)(parts) (parts) (parts) (parts) 1 TEXIN DP7-3005 EPIKOTE 828 2.72 0.42 —— — (67.80) (29.06) 2 TEXIN DP7-3005 EPIKOTE 828 4.44 0.69 — — — (47.43)(47.43) 3 TEXIN DP7-3005 EPIKOTE 828 1.83 0.28 — — — (78.31) (19.58) 4DESMOPAN KU2-8600 EPIKOTE 828 2.72 0.42 — — — (67.80) (29.06) 5 DESMOPANKU2-8600 EPIKOTE 828 4.44 0.69 — — — (47.43) (47.43) 6 TEXIN DP7-3006EPIKOTE 828 2.67 0.41 — — — (64.58) (31.66) 7 TEXIN DP7-3007 EPIKOTE 8282.72 0.42 — — — (67.80) (29.06) 8 MORTHANE PE 192-100 EPIKOTE 828 2.720.42 — — — (67.80) (29.06) 9 MORTHANE PE 193-100 EPIKOTE 828 2.72 0.42 —— — (67.80) (29.06) 10 MORTHANE PE 299-100 EPIKOTE 828 2.72 0.42 — — —(67.80) (29.06) 11 PEARLTHANE 125 EPIKOTE 828 2.72 0.42 — — — (67.80)(29.06) 12 PEARLTHANE 126 EPIKOTE 828 2.72 0.42 — — — (67.80) (29.06) 13MORTHANE PN 03 214 EPIKOTE 828 2.72 0.42 — — — (67.80) (29.06) 14DESMOPAN KU2-8600 EPONEX DRH 1510 2.72 042 — — — (67.80) (29.06) 15DESMOPAN KU2-8600 DEN 431 2.72 0.42 — — — (67.80) (29.06) 16 DESMOPANKU2-8600 DEN 438 2.72 0.42 — — — (67.80) (29.06) 17 TEXIN DP7-3005EPONEX DRH 1510 2.72 0.42 — — — (67.80) (29.06) 18 TEXIN DP7-3005 DEN431 2.72 0.42 — — — (67.80) (29.06) 19 TEXIN DP7-3005 DEN 438 2.72 0.42— — — (67.80) (29.06) 20 TEXIN DP7-3005 EPIKOTE 828 4.20 0.64 AEROSIL200 — — (61.54) (33.14) (0.47) 21 TEXIN DP7-3005 EPIKOTE 828 4.18 0.64AEROSIL 200 — — (61.25) (32.98) (0.94) 22 TEXIN DP7-3005 EPIKOTE 8284.14 0.63 AEROSIL 200 — — (60.68) (32.67) (1.87) 23 DESMOPAN DU2-8600EPIKOTE 828 4.18 0.64 AEROSIL R-972 — — (61.25) (32.98) (0.94) 24 TEXINDP7-3006 EPIKOTE 828 4.00 0.60 — KRATON — (60.00) (30.00) L1203 (5.40)25 TEXIN DP7-3006 EPIKOTE 828 4.07 0.62 — KRATON — (61.10) (30.54) L2203(3.67) 26 TEXIN DP7-3006 EPIKOTE 828 4.01 0.61 AEROSIL R-972 KRATON —(60.27) (30.13) (1.36) L2203 (3.62) 27 TEXIN DP7-3006 EPIKOTE 828 3.870.59 AEROSIL 200 KRATON — (58.17) (29.08) (1.31) L1203 (6.98) 28DESMOPAN KU2-8600 EPIKOTE 828 4.03 0.62 — — A-187 (59.03) (31.78)(0.91), TFA (3.63) 29 TEXIN DP7-3005 EPIKOTE 828 4.03 0.62 — — A-187(59.03) (31.78) (0.91), TFA (3.63) 30 TEXIN DP7-3006 EPIKOTE 828 4.140.63 — — Glycerine (62.24) (31.11) (1.87) — Means that this material wasnot present

Sealant Compositions 31 to 34

Sealant compositions 31 to 34 were prepared in the same manner asdescribed in conjunction with sealant compositions 1 to 30 except usingmixtures of two different thermoplastic polyurethane components as shownbelow in Table 2.

TABLE 2 Thermoplastic Thermoplastic Epoxy- Polyurethane PolyurethaneContaining Sealant Component 1 Component 2 Material Curative AcceleratorComposition (parts) (parts) (parts) (parts) (parts) 31 DESMOPANDESMOCOLL EPIKOTE 4.22 0.65 KU2-8600 406 828 (33.30) (33.30) (28.53) 32DESMOPAN DESMOCOLL EPIKOTE 4.22 0.65 KU2-8600 406 828 (49.94) (16.65)(28.53) 33 DESMOPAN DESMOCOLL EPIKOTE 4.22 0.65 KU2-8600 500 828 (33.30)(33.30) (28.53) 34 DESMOPAN DESMOCOLL EPIKOTE 4.22 0.65 KU2-8600 500 828(49.94) (16.65) (28.53)

Example 1

Example 1 shows the effect on the Melt Flow and Low Temperature (Temp.)Flexibility Tests by varying the type of epoxy-containing material. Thetypes and amounts of all other components remained constant. Thethermoplastic polyurethane used in these formulations is one preferredmaterial, TEXIN DP7-3005. The results are shown in Table 3.

TABLE 3 Cured Sealant Epoxy- Uncured Sealant Composition SealantContaining Composition Low Temp. Composition Material Melt Flow (mm)Flexibility  1 EPIKOTE 828  35* Pass 17 EPONEX 81 Pass DRH 1510 18 DEN431 36 Pass 19 DEN 438  5 Pass *Tested at 150° C. All other sealantcompositions tested at 177° C.

In addition, sealant composition 1, while uncured, had an 180° peeladhesion of 1.65 N/2.54 cm. Once cured, sealant composition 1 displayedan overlap shear strength of 4.9 N/mm² to abraded aluminum and 8.1 N/mm²to unabraded aluminum. It also gave an acceptable appearance in theSimulated Roof Ditch Test. These tests were carried out as describedabove.

Example 2

This example shows the effect on the melt flow (measured as describedabove) of the uncured sealant composition by varying the type ofepoxy-containing material. The results are illustrated in Table 4. Thetypes and amounts of the other components remained constant. Thethermoplastic polyurethane component used in these formulations wasanother preferred material, DESMOPAN KU2-8600. Each of the sealantcompositions, when cured, passed the Low.Temperature Flexibility Testdescribed above.

TABLE 4 Uncured Sealant Sealant Epoxy-Containing Composition CompositionMaterial Melt Flow (mm)*  4 EPIKOTE 828 35 14 EPONEX DRH 1510 52 15 DEN431 16 16 DEN 438  0 *Tested at 177° C.

Example 3

This example shows the effect on melt flow and 180° peel adhesion forthe uncured sealant composition, and on the low temperature (temp.)flexibility of the cured sealant composition by varying the weight ratioof thermoplastic polyurethane component to epoxy-containing material(referred to as “Ratio” in Table 5). The results are presented in Table5. At high levels of epoxy-containing material, the cured sealantcomposition was brittle and failed the Low Temperature Flexibility Test.The test procedures were carried out as described above.

TABLE 5 Uncured Sealant Composition Cured Sealant Melt 180° PeelComposition Sealant Flow Adhesion Low Temp. Composition Ratio (mm)(N/2.54 cm) Flexibility 3 2.42 17* 2.27 Pass 1 2.33 35* 1.65 Pass 2 1.0075* 0.61 Fail 4 2.33 35  — Pass 5 1.00 45  — Fail *Tested at 150° C. Allother sealants were tested at 177° C. — means not measured

Example 4

This example shows the influence of the hardness of the thermoplasticpolyurethane component and of the type of soft segment used therein(polyether or polyester) on the low temperature (temp.) flexibilityproperties of the cured sealant compositions. The test was performed asdescribed above and with the results given in Table 6.

TABLE 6 Sealant Thermoplastic Polyurethane Low Temp. Composition TypeHardness Flexibility 4 Polyether Shore D = 31 Pass Shore A = 82 1Polyether Shore D = 43 Pass Shore A = 83 7 Polyether Shore D = 58 Fail 8Polyether Shore A = 76 Pass 9 Polyether Shore A = 74 Pass 10 PolyetherShore A = 75 Pass 11 Polyester Shore D = 36 Fail 12 Polyester Shore D =42 Fail

Example 5

This example demonstrates the effect of adding silica to the sealantcompositions of the invention and then testing according to thepreviously described methods. The results are presented in Table 7.

TABLE 7 Cured Sealant Uncured Sealant Composition Sealant CompositionLow Temp. Water Composition % Silica Melt Flow (mm)* FlexibilityResistance 20 0.47 31 Pass Pass 21 0.94 18 Pass Pass 22 1.87 1 Pass Pass*Tested at 177° C.

Example 6

This example shows the effect of using 4,4,4,-trifluoro-1s(2-thienyl)-1,3-butanedione chelating agent as described inTable 8 and according to the test procedures described above.

TABLE 8 Uncured Sealant Cured Sealant Sealant Composition CompositionComposition Melt Flow (mm)* Water Resistance 28 43 Pass 29 53 Pass*Tested at 177° C.

Example 7

This example and the results illustrated in Table 9 show that athermoplastic polyurethane component derived from a polyether polyol andhaving a relatively low softening temperature can be effectively blendedwith a thermoplastic polyurethane component derived from a polyesterpolyol and having a relatively high softening temperature to achievesealant compositions according to the invention. The tests wereconducted according to the procedures described above.

TABLE 9 Uncured Sealant Cured Sealant Sealant Composition CompositionComposition Melt Flow (mm)* Low Temp. Flexibility 31 57 Fail 32 41 Pass33 79 Fail 34 59 Pass *Tested at 177° C.

Example 8

This example shows the relationship between phase separation that occursin cured sealant compositions according to the invention and lowtemperature flexibility properties. Sealant compositions 11 and 12(which included a thermoplastic polyurethane derived from a polyesterpolyol) did not phase separate upon curing, while sealant compositions 1and 4, which are typical of all of the samples that passed the LowTemperature Flexibility Test, did phase separate upon curing. Other testresults are given in Table 10. All tests were conducted according to thepreviously described procedures.

TABLE 10 Phase Cured Sealant Sealant Separation Upon CompositionComposition Curing Low Temp. Flexibility 1 Yes Pass 4 Yes Pass 11 NoFail 12 No Fail

Example 9

This example and Table 11 show the results of testing (as describedabove) of other sealant compositions.

TABLE 11 Cured Sealant Composition Uncured Sealant Simulated SealantComposition Low Temp. Roof Ditch Composition Melt Flow (mm)* Flexibility(appearance) 6 43 Fail OK 13 — Fail — 17 81 Pass — 18 36 Pass — 19 5Pass — 23 9 Pass — 24 34 Fail OK 25 40 Fail OK 26 27 Fail OK 27 25 FailOK 30 37 Fail — *Tested at 177° C. — Not tested

Examples 6 and 24-27 and 30 were based on a sealant composition thatincorporated a thermoplastic polyurethane component that had a Shore Dhardness equal to 50, and which demonstrated a Tan δ peak (DMTAanalysis) having an amplitude of less than 0.05 unit in the lowtemperature range between −50 to 0° C.

Sealant compositions 24, 25 and 30 passed the water resistance test. Theother sealant compositions in this table were not evaluated under thistest.

Example 10

A sealant composition was prepared by compounding a blend comprising 40parts of a thermoplastic polyurethane component (ET370), 10 parts of apolyester compound (DYNAPOL S 1402), and 40 parts of an epoxy-containingmaterial (EPIKOTE 1001F) at a temperature setting of 160° C., extrudingthe blend into strands, and pelletizing the strands using a 15 mm twinscrew continuous compounding single zone extruder (MP-2015 Benchextruder manufactured by APV Chemical Machinery, Inc., U.S.A. Aftercooling, 90 parts of the pellets were extruded with 10 parts of an epoxycurative mixture having 2 parts of dicyandiamide (available from ACR Co.Ltd., Tokyo, Japan) and 1 part 2MZA using the same extruder at atemperature setting of 110° C. The extrudate was immediately knifecoated between two silicone-coated PET release liners to form a sheet ofsealant composition having a thickness of 2.0 mm. The sheet was thencooled to room temperature (about 23° C.). The resulting sheet was cutinto appropriate sized sections and tested following the proceduresdescribed above, with the results shown below in Table 12.

Example 11

A sealant composition was prepared and tested according to the methoddescribed in Example 10 except that the sealant composition included 50parts of ET370, 40 parts of EPIKOTE 1001F, and 10 parts of the epoxycurative mixture. Test results are shown in Table 12.

Example 12

A sealant composition was prepared and tested according to the methoddescribed Example 10 except that the thermoplastic polyurethanecomponent was provided by ET880. Test results are shown in Table 12.

TABLE 12 Test Procedure Simulated Cold Seam Temperature Temperature 250Hour Example Sealing Cycle Aging Elongation Water Soak 10 Good Good 70%Good 11 Fair Good 70% (brittle) Good 12 Poor Good 25% (brittle) Good

Example 13

A first sealant composition was prepared according to the proceduredescribed in Example 10, except that the extruder was set at atemperature of 100° C. and the blend comprised 60 parts of a polyestercomponent (DYNAPOL S1402), 30 parts of an epoxy-containing material(Epoxy Resin I), and 10 parts of an epoxy curative mixture. The epoxycurative mixture contained 70 parts of H3636AS and 30 parts of 2MZA. Theextruded composition was immediately knife coated to a thickness of 1.5mm between two silicone coated PET release liners to form the firstlayer of a multilayer sealing tape.

Pellets of a second sealant composition were prepared according to theprocedure described in Example 10 except that the blend comprised 40parts of thermoplastic polyurethane component (ET370), 50 parts of anepoxy-containing material, and 3.5 parts of calcium carbonate. Theepoxy-containing material was a mixture of 20 parts of EPIKOTE 1004K and30 parts of EPIKOTE 828. After cooling, 93.5 parts of these pellets wereextruded with 6.5 parts of an epoxy. curative mixture having 10 parts ofH3636AS and 3 parts of 2MZA. The second sealant composition wasimmediately knife coated to a thickness of 2.0 mm between two siliconecoated PET release liners to form the second layer of a multilayersealing tape.

A 3.7 mm thick multilayer sealing tape was prepared by laminating a 0.44mm thick polyester non-woven fabric with a basis weight of 100g/m²(MARIX21008WTV available from Yunichika, Osaka, Japan) between the firstand second layers of sealant composition, taking care to prevent airentrapment during the lamination.

A 150 micrometer thick, double-side surface treated PET film (availableas OPF film from Teijin, Osaka, Japan) was then laminated to the exposedsurface of the second layer of sealant composition to provide apaintable surface. The multilayer sealing tape was tested according tothe Lap Joint Sealing and Sealant Composition Surface Appearance Testsdescribed above and with the results shown below in Table 13.

Example 14

A 3.8 mm thick multilayer sealing tape was prepared and tested accordingto the procedures and sealant compositions described for Example 13,except that the nonwoven fabric layer was provided by a 0.50 mm thickpolyester nonwoven material having a basis weight of 100 g/m² (Smashavailable from Asahi Kasei, Osaka, Japan).

Example 15

A 3.5 mm thick multilayer sealing tape was prepared by laminating three1.0 mm thick layers of sealant composition (prepared according to theprocedures and composition for the second sealant composition describedin Example 13) with a layer of a polyester nonwoven fabric(MARIX21008WTV) between each layer of sealant composition. Themultilayer sealing tape had the following construction: sealantcomposition/nonwoven fabric/sealant composition/nonwoven fabric/sealantcomposition.

The PET film described in Example 13 was then laminated to one side ofthe multilayer sealant tape.

TABLE 13 Uncured Sealant Composition Test Methods Example Lap JointSealing Surface Appearance 13 Good Flat, no depressions overindentations 14 Good Flat, no depressions over indentations 15 GoodFlat, no depressions over indentations

Various modifications of the foregoing description will be apparent tothose skilled in the art without departing from the invention, which isdefined by the appended claims:

What is claimed is:
 1. A sealant article comprising: a) a layer of asealant composition comprising: i) a curable epoxy-containing material;ii) a first thermoplastic polyurethane component that is thepolymerization product of a polymerizable mixture comprising apolyisocyanate and a polytetramethylene oxide polyol; iii) a curativefor-the epoxy-containing material; and iv) optionally, a secondthermoplastic polyurethane component that is different than the firstthermoplastic polyurethane component;  wherein the composition providesa melt-flowable sealant for sealing discontinuities in the surface of asubstrate; and b) another layer attached to the sealant compositionlayer of part a) which other layer is selected from the group consistingof: woven webs, non-woven webs, scrims, and metal caps.
 2. A compositioncomprising: a) a curable epoxy-containing material; b) a firstthermoplastic polyurethane component; c) a curative for theepoxy-containing material; and d) a second thermoplastic polyurethanecomponent that is different than the first thermoplastic polyurethanecomponent;  wherein components (a), (b) and (d) display only asingle-phase upon melt blending, but the composition is phase-separatedafter curing;  said composition being characterized by both polyetherand polyester thermoplastic polyurethanes being used in which the weightratio of polyether polyurethane to polyester lethane is greater than 1.3. The sealant article according to claim 1 wherein the sealantcomposition is tacky at a temperature of about 15 to 25° C.
 4. Thesealant article according to claim 1 wherein the sealant composition hasat least one glass transition temperature of less than −20° C.
 5. Thesealant article according to claim 1 wherein the first thermoplasticpolyurethane component has a Shore D hardness of less than 50 or a ShoreA hardness of less than
 85. 6. The sealant article according to claim 1wherein the sealant composition comprises: i) about 20 to 40 weightpercent of the epoxy-containing material; and ii) about 60 to 80 weightpercent of all thermoplastic polyurethane components present in thecomposition; wherein the sum of (i) and (ii) is 100 weight percent.
 7. Acomposition according to claim 2 wherein the first thermoplasticpolyurethane component is the polymerization product of a polymerizablemixture comprising a polyisocyanate and polyether polyol.
 8. The sealantarticle according to claim 1 wherein the polytetramethylene oxide polyolfor the first thermoplastic polyurethane component has a number averagemolecular weight of at least
 600. 9. The sealant article according toclaim 8 wherein the polyisocyanate for the first thermoplasticpolyurethane component is an aliphatic diisocyanate.
 10. The sealantarticle according to claim 1 wherein the polytetramethylene oxide polyolfor the first thermoplastic polyurethane component has a number averagemolecular weight of at least
 1000. 11. The sealant article according toclaim 10 wherein the polyisocyanate for the first thermoplasticpolyurethane component is an aromatic diisocyanate.
 12. An articlecomprising a surface having a discontinuity formed thereon, and a layerof a sealant article comprising: a) a layer of a sealant compositioncomprising: i) a curable epoxy-containing material; ii) a firstthermoplastic polyurethane component that is the polymerization productof a polymerizable mixture comprising a polyisocyanate and apolytetramethylene oxide polyol; iii) a curative for theepoxy-containing material; and iv) optionally, a second thermoplasticpolyurethane component that is different than the first thermoplasticpolyurethane component;  wherein the composition provides amelt-flowable sealant for sealing discontinuities in the surface of asubstrate; and b) another layer attached to the sealant compositionlayer of part a) which other layer is selected from the group consistingof: woven webs, non-woven webs, scrims, thermoplastic film, metal capsand plastic caps, the sealant composition of which has been cured andwhich seals the discontinuity.
 13. The article according to claim 12wherein the polymerizable mixture for the first thermoplasticpolyurethane component comprises: a) an aliphatic diisocyanate, apolytetramethylene oxide polyol that has a number average molecularweight of at least 600, and a diol chain extending agent; or b) anaromatic diisocyanate, a polytetramethylene oxide polyol that has anumber average molecular weight of at least 1000, and an diol chainextending agent.
 14. The sealant article according to claim 13 whereinthe curative for the epoxy-containing material is dicyandiamide.
 15. Thesealant article according to claim 14 wherein the sealant compositionfurther comprises an imidazole accelerator.
 16. A method of sealing adiscontinuity in the surface of a substrate, the method comprising thesteps of: a) placing over the discontinuity, a sealant compositioncomprising i) a curable epoxy-containing material; ii) a firstthermoplastic polyurethane component that is the polymerization productof a polymerizable mixture comprising a polyisocyanate and apolytetramethylene oxide polyol; iii) a curative for theepoxy-containing material; and iv) optionally, a second thermoplasticpolyurethane component different from the first thermoplasticpolyurethane component; b) heating the sealant composition to cause thecomposition to flow and seal the discontinuity; and allowing the sealantcomposition to cool.
 17. A method according to claim 16 furthercomprising the step of heating the sealant composition for a time and ata temperature sufficient to fully cure the sealant composition.